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Mercury Exposure and Autistic Behavior: No Link?

The chemical is often found in fish, prompting many pregnant women to avoid the food

WebMD News Archive

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Eating fish during pregnancy can present a dilemma for expectant mothers and their doctors. Fish are high in a number of beneficial nutrients, including some that are essential to brain development. However, fish can contain mercury, and high levels of mercury have been shown to lead to developmental problems in children.

Although the impact of low level exposure to mercury on children remains unknown, some organizations, including the U.S. Food and Drug Administration, recommend that pregnant women limit their consumption of fish, the study authors noted.

But is that caution necessary, the study authors wonder?

"This study shows no consistent association in children with mothers with mercury levels that were six to 10 times higher than those found in the U.S. and Europe. This is a sentinel population and if (the association between low-level mercury exposure and autism) does not exist here than it probably does not exist," Philip Davidson, principal investigator of the Seychelles Child Development Study and professor emeritus in pediatrics at the University of Rochester Medical Center, said in the news release.

The finding lends support to an emerging belief that the good may outweigh the possible bad when it comes to eating fish during pregnancy. Specifically, if the mercury did not harm brain development at the levels of exposure experienced by the children in this study, then the benefits of the nutrients in fish may counteract or surpass the potential negative effects of mercury, the study authors said.

One autism expert said changes to dietary recommendations are unlikely.

"Although fish is generally viewed as an excellent dietary choice, women have been advised to limit fish consumption when pregnant," said Dr. Andrew Adesman, chief of developmental & behavioral pediatrics at Cohen Children's Medical Center of New York in New Hyde Park, NY.

Even though the study showed no mercury-autism link, "it is unlikely that dietary recommendations will be revised in light of this study alone," he said.

Funding for the study was provided, in part, by the U.S. National Institute of Environmental Health Sciences (NIEHS), part of the U.S. National Institutes of Health.

"NIEHS has been a major supporter of research looking into the human health risks associated with mercury exposure," Cindy Lawler, acting branch chief at the National Institute of Environmental Health Sciences, said in the news release. "The studies conducted in the Seychelles Islands have provided a unique opportunity to better understand the relationship between environmental factors, such as mercury, and the role they may play in the development of diseases like autism. Although more research is needed, this study does present some good news for parents."